

/* @(#)w_pow.c 5.2 93/10/01 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/*
FUNCTION
    <<pow>>, <<powf>>---x to the power y
INDEX
    pow
INDEX
    powf


ANSI_SYNOPSIS
    #include <math.h>
    double pow(double <[x]>, double <[y]>);
    float powf(float <[x]>, float <[y]>);

TRAD_SYNOPSIS
    #include <math.h>
    double pow(<[x]>, <[y]>);
    double <[x]>, <[y]>;

    float powf(<[x]>, <[y]>);
    float <[x]>, <[y]>;

DESCRIPTION
    <<pow>> and <<powf>> calculate <[x]> raised to the exponent <[y]>.
    @tex
    (That is, $x^y$.)
    @end tex

RETURNS
    On success, <<pow>> and <<powf>> return the value calculated.

    When the argument values would produce overflow, <<pow>>
    returns <<HUGE_VAL>> and set <<errno>> to <<ERANGE>>.  If the
    argument <[x]> passed to <<pow>> or <<powf>> is a negative
    noninteger, and <[y]> is also not an integer, then <<errno>>
    is set to <<EDOM>>.  If <[x]> and <[y]> are both 0, then
    <<pow>> and <<powf>> return <<1>>.

    You can modify error handling for these functions using <<matherr>>.

PORTABILITY
    <<pow>> is ANSI C. <<powf>> is an extension.  */

/*
 * wrapper pow(x,y) return x**y
 */

#include "fdlibm.h"
#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
    double pow(double x, double y)  /* wrapper pow */
#else
    double pow(x,y)         /* wrapper pow */
    double x,y;
#endif
{
#ifdef _IEEE_LIBM
    return  __ieee754_pow(x,y);
#else
    double z;
#ifndef HUGE_VAL
#define HUGE_VAL inf
    double inf = 0.0;

    SET_HIGH_WORD(inf,0x7ff00000);  /* set inf to infinite */
#endif
    struct exception exc;
    z=__ieee754_pow(x,y);
    if(_LIB_VERSION == _IEEE_|| isnan(y)) return z;
    if(isnan(x)) {
        if(y==0.0) {
        /* pow(NaN,0.0) */
        /* error only if _LIB_VERSION == _SVID_ & _XOPEN_ */
        exc.type = DOMAIN;
        exc.name = "pow";
        exc.err = 0;
        exc.arg1 = x;
        exc.arg2 = y;
        exc.retval = 1.0;
        if (_LIB_VERSION == _IEEE_ ||
            _LIB_VERSION == _POSIX_) exc.retval = 1.0;
        else if (!matherr(&exc)) {
            Djy_SaveLastError(EDOM);
        }
            if (exc.err != 0)
               Djy_SaveLastError(exc.err);
                return exc.retval;
        } else
        return z;
    }
    if(x==0.0){
        if(y==0.0) {
        /* pow(0.0,0.0) */
        /* error only if _LIB_VERSION == _SVID_ */
        exc.type = DOMAIN;
        exc.name = "pow";
        exc.err = 0;
        exc.arg1 = x;
        exc.arg2 = y;
        exc.retval = 0.0;
        if (_LIB_VERSION != _SVID_) exc.retval = 1.0;
        else if (!matherr(&exc)) {
            Djy_SaveLastError(EDOM);
        }
            if (exc.err != 0)
               Djy_SaveLastError(exc.err);
                return exc.retval;
        }
            if(finite(y)&&y<0.0) {
        /* 0**neg */
        exc.type = DOMAIN;
        exc.name = "pow";
        exc.err = 0;
        exc.arg1 = x;
        exc.arg2 = y;
        if (_LIB_VERSION == _SVID_)
          exc.retval = 0.0;
        else
          exc.retval = -HUGE_VAL;
        if (_LIB_VERSION == _POSIX_)
          Djy_SaveLastError(EDOM);
        else if (!matherr(&exc)) {
          Djy_SaveLastError(EDOM);
        }
            if (exc.err != 0)
               Djy_SaveLastError(exc.err);
                return exc.retval;
            }
        return z;
    }
    if(!finite(z)) {
        if(finite(x)&&finite(y)) {
            if(isnan(z)) {
            /* neg**non-integral */
            exc.type = DOMAIN;
            exc.name = "pow";
            exc.err = 0;
            exc.arg1 = x;
            exc.arg2 = y;
            if (_LIB_VERSION == _SVID_)
                exc.retval = 0.0;
            else
                exc.retval = 0.0/0.0;   /* X/Open allow NaN */
            if (_LIB_VERSION == _POSIX_)
                Djy_SaveLastError(EDOM);
            else if (!matherr(&exc)) {
                Djy_SaveLastError(EDOM);
            }
                if (exc.err != 0)
                    Djy_SaveLastError(exc.err);
                    return exc.retval;
            } else {
            /* pow(x,y) overflow */
            exc.type = OVERFLOW;
            exc.name = "pow";
            exc.err = 0;
            exc.arg1 = x;
            exc.arg2 = y;
            if (_LIB_VERSION == _SVID_) {
               exc.retval = HUGE;
               y *= 0.5;
               if(x<0.0&&rint(y)!=y) exc.retval = -HUGE;
            } else {
               exc.retval = HUGE_VAL;
                       y *= 0.5;
               if(x<0.0&&rint(y)!=y) exc.retval = -HUGE_VAL;
            }
            if (_LIB_VERSION == _POSIX_)
                Djy_SaveLastError(ERANGE);
            else if (!matherr(&exc)) {
            Djy_SaveLastError(ERANGE);
            }
                if (exc.err != 0)
                    Djy_SaveLastError(exc.err);
                    return exc.retval;
                }
        }
    }
    if(z==0.0&&finite(x)&&finite(y)) {
        /* pow(x,y) underflow */
        exc.type = UNDERFLOW;
        exc.name = "pow";
        exc.err = 0;
        exc.arg1 = x;
        exc.arg2 = y;
        exc.retval =  0.0;
        if (_LIB_VERSION == _POSIX_)
            Djy_SaveLastError(ERANGE);
        else if (!matherr(&exc)) {
            Djy_SaveLastError(ERANGE);
        }
        if (exc.err != 0)
            Djy_SaveLastError(exc.err);
            return exc.retval;
        }
    return z;
#endif
}

#endif /* defined(_DOUBLE_IS_32BITS) */














